Hi,
How do you resize and compress (format) the images? If we interpolate depth images like any kind of images this would add depth artefacts. See
util2d::interpolate() for example (there is also
util2d::decimate()). Make sure you are using "image_transport:=compressedDepth" with the depth topic and not "image_transport:=compressed" (which would add jpeg artefacts).
Note that you don't need to resize back the depth image if you want more efficiency. rtabmap can handle combination of RGB images of 640x480 with depth images of 320x240, the conditions are that the camera_info used is the one of the RGB image (default), that original depth images 640x480 were already registered to RGB camera and that depth image size is a integer decimation of the RGB image size (e.g., here is 2x smaller).
cheers